/usr/share/doc/userv/examples/system.override is in userv 1.1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | # This is for subtle overriding things. Most things should go in
# system.default (or default.d or services.d), so that the user can
# override them if they want and so that if you want to force the user
# to provide a service you don't needlessly parse their configuration
# file and get the error messages from it.
include-directory /etc/userv/override.d
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